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Exception Handling

Exception Handling. Shirley Moore CS 1401 Spring 2013 cs1401spring2013.pbworks.com May 7, 2013. Agenda. Announcements Turn in Take- home Quiz 7 String class (for Prog Ex 11.2 and Lab 9) Assess Programming Exercises 11.1, 11.2 UML Class Diagrams (in detail) Exception handling

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Exception Handling

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  1. Exception Handling Shirley Moore CS 1401 Spring 2013 cs1401spring2013.pbworks.com May 7, 2013

  2. Agenda • Announcements • Turn in Take-home Quiz 7 • String class (for Prog Ex 11.2 and Lab 9) • Assess Programming Exercises 11.1, 11.2 • UML Class Diagrams (in detail) • Exception handling • Expectations for Final Exam

  3. Announcements • Women in Engineering (WIN) meeting • Thursday, May 9, 4-6pm • ACES, Classroom Building • Lab 9 • Part I will be graded in lab today (must attend to get grade) • Part 2 on your own before Thursday • Part 3 will be graded in lab on Thursday • Plan to post all grades (hw, labs, etc.) by beginning of next week • Final Exam • Thursday, May 16, 10:00am-12:45pm • CCSB 1.0704 (this room) • Must get 60% on final exam to pass course • Final Exam Review with Peer Leaders • Friday, May 10, 10am-? , CCSB 1.0704 • Turn in research mini-projects by Friday, May 17, at the latest.

  4. String class • The Java String class provides many methods for creating and manipulating strings. • A String object is immutable – i.e., it contents cannot be changed. • Examples (Try and draw a picture to illustrate): • String s1 = new String(“Welcome to Java”); • String s2 = “Welcome to Java”); • String s3 = “Welcome to Java”); • if (s1 == s2) System.out.println(“s1 and s2 are the same object”); • if (s2 == s3) System.out.println(“s2 and s3 are the same object”); • if (s1.equals(s2) System.out.println(“s1 and s2 have the same contents”); • See Chapter 9 and/or http://docs.oracle.com/javase/7/docs/api/java/lang/String.html for more String class methods.

  5. Programming Exercise 11.1 • (The Triangle class) Design a class named Triangle that extends GeometricObject. The class contains: • Three private double data fields side1, side2, side3 with default values of 1. • A no-arg constructor that creates a default triangle. • A constructor that creates a triangle with specified side1, side2, and side3. • The accessor methods for all three data fields. • A method getArea() that returns the area of the triangle • A method getPerimeter() that returns the perimeter of the triangle • A method toString() that returns a string representation of the triangle.

  6. Programming Exercise 11.2 • (The Person, Student, Employee, Faculty, and Staff classes) Design a class named Person and its two subclasses named Student and Employee. Make Faculty and Staff subclasses of Employee. A person has a name, address, phone number, and email address. A student has a class status (freshman, sophomore, junior, senior). Define the status as a constant. An employee has an office, salary, and date hired. A faculty member has office hours and a rank. A staff member has a title. Override the toString method in each class to display the class name and the person’s name.

  7. UML Class Diagrams • See http://cs.nmu.edu/~mkowalcz/cs120f08/uml/UMLdiagram.html

  8. Exception Handling • Enables a program to deal with exceptional (i.e., error) situations and continue operation • Can make programs more reliable • Examples of exceptions • Integer division by zero • Input mismatch (e.g., real number entered when integer was requested) • Illegal argument value • Enable methods to “throw” exceptions back to caller • Why not just have the method print an error message and exit? • Caller uses a try-catch block to invoke the method and handle any exception

  9. Exception Types • Exceptions are objects that are defined using classes. • Pre-defined exception types in java.lang.Throwable class • http://docs.oracle.com/javase/7/docs/api/java/lang/RuntimeException.html • e.g., ArithmeticException, NullPointerException, IndexOutOfBoundsException, IllegalArgumentException • You can also define your own exception types.

  10. Examples • Download from course website: • QuotientWithException.java (trivial example for illustration purposes) • InputMismatchExceptionDemo.java • Circle3.java (also need GeometricObject.java) • Circle4.java • InvalidRadiusException.java • TestCircles.java

  11. Class Activity • Download from course website: • Projectile.java • TestProjectile.java • Modify the program to handle the following exceptions • Invalid input • Initial height must be non-negative • Initial velocity must be positive • Angle of inclination must be greater than 0 and less than 90 • Invalid time step interval (must be positive)

  12. Final Exam • Comprehensive • Will target learning outcomes from each unit • Review guide and practice problems will be posted by tomorrow. • Review in class on Thursday • Review session with Peer Leaders on Friday at 10:00

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